OK I ran across this little snag in a VB.NET application, and thought I might share an easy solution to the problem. If you ever have a .NET solution that originated in a previous version other than 2010 and has been upgraded, you might have some difficulty accessing members of the 'My' namespace. Specifically I was missing the auto generated 'MyWebExtensions.vb' code file displayed below:
This resulted in the "'Application' is not a member of 'My'" error:
There are probably a few tricks you could make to the solution (.sln) file by opening it in Notepad and fixing the appropriate settings, but the easiest way to fix the error is to remove the 'My' extension and add it back into the project. To do this open the project's properties of the project where the error is occurring, and click on the "My Extensions" tab.
The 'My' extension you need for your project is dependent on the type of project you have created (Web, WPF, etc.), so make sure to select the proper one when re-adding. First though, right-click the current extension already added and select “Remove Extension”
Then press the "Add Extension" button in the bottom right-hand corner, and add the appropriate extension back into your project. This should auto-generate the 'MyWebExtensions.vb' code file and fix any previously non-accessible members in the 'My' namespace.
For more information on the 'My' namespace, check out the (2) MSDN links below:
How My Depends on Project Type (Visual Basic)